Method and apparatus for alerting remote personnel of aircraft, location and identification

ABSTRACT

The present invention is directed to the method and apparatus for detecting aircraft, identifying the aircraft as friend or foe, and transmitting alerting signals, the position and identity of the aircraft from a central location to a plurality of remote locations. A radar is used to detect aircraft and identify the aircraft as friend or foe. The position of the aircraft is disclosed on a plan position indicator (PPI). An operator transfers the information (position and identity) on the PPI to a plugboard by placing an appropriate plug in the plugboard to indicate the aircraft as friend or foe and to show the location of the aircraft. The information from the plugboard is encoded and transmitted to a plurality of remote locations. The information received at the remote locations is decoded and displayed such that an operator at the remote location may determine the location and identity of the aircraft detected by the radar.

United States Patent [72] Inventor John A. French 3,159,831 12/1964 Muth343/6.5X g g n Primary Examiner-Rodney D. Bennett, Jr. P Se 1969Assistant Examiner-Malcolm F. Hubler [22] Ffled Attomeys-Harry M.Saragovitz, Edward J. Kelly, Herbert [45 1 Patented 1971 Berl and AubreyJ. Dunn [73] Assignee States of America as represented by the Secretaryof the Army ABSTRACT: The present invention is directed to the method[54] ?X?d apparatus forddetecting aircrzlft, identifying the aircraft asAND IDENTIFICATION men or oe, an t ransmming ertmg signals, the posltion5 Claim 1 Drawin Fig and 1dent1ty of the a1rcraft from a centrallocation to a pluralig ty of remote locations. A radar is used to detectaircraft and ,[52] US. Cl. 343/6, ide tif the aircraft as friend or foe.The position of the air- 7 V 343/65 craft is disclosed on a planposition indicator (PPI), An opera- [51] Int. Cl. G01s 7/12, tortransfers the information (position and identity) on the PP] G018 to aplugboard by placing an appropriate plug in the plugboard [50] FieldofSearch 343/6, 6 to indicate the aircraft as friend or foe and to showthe location of the aircraft. The information from the plugboard isencoded and transmitted to a plurality of remote locations. The [56]References cued information received at the remote locations is decodedand UNITED STATES PATENTS displayed such that an operator at the remotelocation may 2,691,162 10/1954 Geer 343/6.5 determine the location andidentity of the aircraft detected by 2,961,485 11/1960 Hentschel(343/6A) th ada REMOTE LOCATION DISPLAY Y PANEL 2 I4- RCVR 1 1 1 22 :2s7 WEAPON POSITION 1 CENTRAL LOCATION PLUGBOARD 7 I l CODE VTR 32GENERATOR XM 12 SWTCHES senor: LOCATION UISPLAY PANEL DECODER MATRIX 3OWEAPON POSITION 2 Patented April 6, 1971 3,573,823

REMOTE LOCATION DISPLAY Y PANEL DECODER 2 I4 RCVR 22 MATRIX o oo T 28WEAPON POSITION 1 CENTRAL LOCATION IO PLUGBOARD 7 Y CODE 7 x GENERATORXMTR l2 32 O O 0O 0O PPI ALERT 6 26 STATUS SWITCHES REMOTE LOCATIONDISPLAY Y PANEL 24 DECODER g", mm MATRIX 30 WEAPON POSITION 2 John A.French,

INVENTOR METHOD AND APPARATUS FOR ALERTING REMOTE PERSONNEL OFAIRCRAFI,LOCATION AND IDENTIFICATION BACKGROUND OF THE INVENTION The problem ofprotecting field military elements against aircraft involves detectingaircraft and identifying the aircraft as friend or foe. Manyantiaircraft weapons rely on the capability of operating troops toinitially detect aircraft visually or audibly. After the aircraft isdetected it must be identified as friendly or hostile before it is firedupon by the troops. Several problems are extant in this manual mode ofoperation. First, operator fatigue is known to reduce alertness afteronly a few hours of duty. Second, weather and physical obstructions willreduce operator effectiveness in spotting aircraft. Third, after anaircraft is spotted, it is extremely difficult to determine itsidentity. Use of profile recognition is largely unsatisfactory becauseof speeds, profile similarities between enemy and friendly planes, anddistances over which identification is desired.

Methods for overcoming these difficulties generally include twocategories or methods of using radar and Identification, Friend or Foe(IFF) equipment. These categories suffer from the problems associatedwith large numbers of sophisticated equipment. The cost of the equipmenttends to become prohibitive when the environment of the forward mobileelements of the military is considered. Logistics factors of supply,repair, maintenance, transport, operation, etc., are much worse than,for example, a radar which is located permanently at a military base.One method employs a radar and [FF at each battery, e. g., each gun orguided missile location. This method would approximately double the costand logistic factors of the battery since a radar is more expensive anddifficult to maintain than other battery equipment. A second methodwould employ a fewer number of centrally located radars which wouldtransmit data to the individual batteries. The seeming economic andlogistic advantages of this approach have been largely lost in the pastby the sophisticated equipment designs that have been necessary. Forexample, large radar equipments have required many operators to trackaircraft with high precision. Aircraft track data is often inserted intocomputers and automatically processed. Target returns are compared toIFF returns and individual aircraft are designated as friend or foe.Either by automatic processing or manual calculations, decisions aremade to assign targets to specific batteries. Following this, precisionhigh capacity communications are utilized to send the information tobatteries. Fire coordination systems of this type have been developedand found to be too expensive and cumbersome to be used for forwardmilitary elements.

It is an object of this invention to provide a method and a systemwhereby aircraft may be detected and identified as friend or foe, andwhereby the position and identification of the aircraft may be promptlytransmitted to remotely located weapons systems and whereby theoperating crews of the weapons systems may be alerted to the presence ofthe aircraft.

SUMMARY OF THE INVENTION The present invention is directed to the methodand apparatus for detecting aircraft, identifying the aircraft as friendor foe, and transmitting alerting signals position and identity of theaircraft from a central location to a plurality of remote locations. Aradar is used to detect aircraft and identify the aircraft as friend orfoe. The position of the aircraft is disclosed on a plan positionindicator (PPI). An operator transfers the information (position andidentity) on the PPI to a plugboard by placing an appropriated plug inthe plugboard to indicate the aircraft as friend or foe and to show thelocation of the aircraft. The information from the plugboard is encodedand transmitted to a plurality of remote locations. The informationreceived at the remote locations is decoded and displayed such that anoperator at the remote location may determine the location and identityof the aircraft detected by the radar.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE drawing is aschematic diagram of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Radar 2 incorporates anIdentification, Friend or Foe (IFF) system and provides signals to thePlan Position Indicator (PPI) display oscilloscope 4. A grid overlay 6,or other method of sectoring the PPI scope, divides the area covered bythe scope into easily recognizable segments corresponding to mapcoordinates of the land immediately surrounding the radar. An operatorobserves target returns and IFF responses on the PPI and determines inwhich segment of the grid overlay the target or targets are located. Agrid-type matrix 32 corresponding to grid overlay 6 is inscribed onplugboard 8. The operator inserts a coded plug 7 into plugboard 8 toindicate aircraft in the position or positions indicated on the PPI. Onetype coded plug indicates a friend while another type indicates a foe asdetermined by the IF response on the PPI. (Other methods orsubstitutions for the plugboard will work equally well. For example, amatrix of switches would be acceptable.) The identity and location ofthe aircraft indicated on the plug board are encoded by code generator10 and transmitted by transmitter 12 to a plurality of weapon sites. Thetransmitted information is received by radio receivers 14 and 16 whichare located at remote weapon sites. Decoders 18 and 20 translate thedata received and initiate display panels 22 and 24. Display panels 22and 24 may be as a matrix of lights or use of any of a number of otherindirect techniques. The remote displays will correspond exactly toplugboard 8 in terms of number, identity and location of targets.Display panels 22 and 24 are oriented by an operator by use of compass30 to be the same as compass 34 on plugboard 8 and PPI 4. The respectivelocation of the receiving remote weapon position may be indicated on thedisplay panel by an X as shown in the drawing. The radar's location mayalso be denoted on the display panels by an appropriate symbol, i.e. A.The weapons operator is now collimated with the radar and the broadcastdata. Any indication on the display panel will appear at the correctrange and bearing as viewed from the weapon site X.

As new targets appear or old targets change position, the radar operatorinserts new data via the plugboard and removes the out-of-date plugs.Alarm or alert status switches 26 provide additional inputs to codegenerator 10 and thereby permit certain commands and conditions to betransmitted to display panels 22 and 24. Lights 28 indicate thepositions of the alert status switches 26. (Audible alarms or othermethods or substitutions for the lights will work equally well.)

The previous disclosure has dealt with four basic functions: detectingaircraft, identifying aircraft, alerting remote operators, anddisplaying the position and identity of the aircraft at a remotelocation. The following disclosure will deal particularly with thefourth function, displaying the position and identity of the aircraft ata remote location. The aircraft's location and identity is determined ata central location. The aircraft's location and identity is thencommunicated to a plurality of remote locations. Standard radiocommunications equip ment with capability of data transmission may beused to transmit the information from the central location to the remotelocations.

Plugboard 8 has a grid system 32 inscribed on its face and is capable ofaccepting plug-type inserts 7 at each intersection of the gridcoordinate system. A hole is provided at the intersection of each of thegrid coordinates. As aircraft appear. and move across the face of thePPI scope, an operator inserts plugs 7 at the corresponding coordinateposition, removing the plugs and reinserting them as the aircraftprogresses. The plugs furnish a means of making electrical contact witha code generator matrix on the underside of the plugboard. To identifyan aircraft at a particular coordinate the operator simply inserts theappropriate plug to indicate position and identity of the aircraft. Twotypes of plugs are provided for use in denoting the identity of theaircraft, i.e. red for foe and blue for friend. The plugs are physicallydifferent, one being longer than the other to thus provide an additionalcontact in the plugboard for indicating a foe. As the plug is insertedinto the hole, a spring contact (in the case of a foe, two or morecontacts) is moved to complete a circuit and thus cause a codecorresponding to this pair of grid coordinates to be generated by thecode generator. If a longer plug is inserted to indicate a foe, theextra length of the plug would permit the tip of the plug to pass onthrough the first spring contacts and reach a second layer of contactsin the plugboard and thus cause the code generator to generate a code toindicate the aircraft as a foe. At the center of the plugboard is arepresentation of the radar location a. This location marker may beoffset to match any offset of the radar sweep itself with respect to therelative position of the radar.

The conductors from the contacts in the plugboard matrix are connectedto code generator 10. A number of wires pass from plugboard 8 to codegenerator 10, the number being determined by the number of gridintersections provided in the plugboard. The code generator senses theposition of the closed contacts on the grid intersection wires and thusthe positions having plugs inserted therein. By logical circuitry thesignals are encoded by the code generator into a corresponding binarycode for that grid position. The code generator also contains a counterwhich scans all the wires and sends out repetitively the codes for thosewires which are energized. The repetition rate for the code groups maybe approximately 20 times per second and still allow up to 16 aircraftto be handled within the time frame of the system. A communications-typetransmitter with capability of data transmission receives the modulationfrom the code generator and sends out coordinate positions repetitively.lf security measures are required, an additional encoding device may beused prior to transmitting the coded information. Similar techniques canbe applied to the alarms or alert status indicator.

There are a number of types of communications equipment which would besuitable for use as the transmitter-receiver link. The transmittershould be capable of both voice and data transmission in order to serveall communication needs. However, if voice communications are notdesired, the size and weight of the transmitter and receiver may beappreciably reduced. The principle requirement of the transmitter andreceiver is that they be capable of handling data transmission at thedata rates required by the system.

The decoder matrix 18 and 20 accepts each grid coordinate code as itcomes from receiver 14 and 16, respectively, in sequence. Translation todisplay panel lamp position is performed in the opposite manner as inthe code generator. The output of the decoder matrix corresponds to oneof the grid intersections on the display panel. No memory need beprovided in the decoder matrix since the coordinate codes are repeatedin sequence at the system rate of 20 times per second. The decodercircuits are time shared by all the multiple targets thus reducing thecost and complexity of the system. This type of operation will produce asteady lamp indication at the location of the aircraft. For a flashingindication, indicative of a foe, the code generator at the centrallocation is designed such that the output of the codes for a foe willonly occur about four times per second. At this rate, a definiteflashing will be visible, contrasted to a steady indication for friendlyaircraft produced by use of the shorter plug in plugboard 8.

The display panel may be any lightweight device consisting of a smallboard with as many lamps inserted as there are intersections of the gridcoordinates thereon and likewise on the plugboard. A separate circuitfor each lamp passes from the decoder matrix to the panel to light thelamp when the line is energized. Depending on the particular design ofthe decoder matrix lamp drivers, the lamps may be either neon orincandescent.

I claim:

1. A method for detecting aircraft and identifying the aircraft asfriend or foe, and transferring the alerting data, location and identityof the aircraft to a plurality of remote locations comprising the stepsof: detecting aircraft with a radar; identifying the aircraft as friendor foe; encoding and transmitting the position and identity and alertstatus of the aircraft to a plurality of remote locations; receivingsaid encoded position, identity, and alert status of the aircraft;decoding the received information and displaying the received aircraftposition and identity and alert status.

2. A method as set forth in claim 1 wherein the step of encoding theposition and identity of the aircraft includes the steps of placing aplug in a plugboard to indicate the position and identity of theaircraft, and encoding the information shown on the plugboard so it maybe transmitted.

3. A method as set forth in claim 1 wherein the step of displaying thereceived position and identity of the aircraft includes the step oflighting a light in a matrix of lights to thereby indicate the positionand identity of the aircraft.

4. A device for transfer of information from a first location to aplurality of second locations comprising: a plugboard; a first andsecond plurality of plugs for insertion in said plugboard; a codegenerator for encoding the position and identity of said plugs insertedin said plugboard, said first plurality of plugs indicating a friendlyaircraft and said second plurality of plugs indicating a foe; means fortransmitting said encoded position and identity of said aircraft; meansfor receiving and decoding said encoded position and identity of saidaircraft; means for displaying the decoded information indicating theposition and identity of said aircraft.

5. A device as set forth in claim 4 wherein said means for displayingthe decoded information comprises a display panel having a matrix oflights thereon, each of said lights being responsive to the position andidentity of said plug inserted in said plugboard whereby the positionand identity of an aircraft may be ascertained by viewing said displaypanel.

1. A method for detecting aircraft and identifying the aircraft asfriend or foe, and transferring the alerting data, location and identityof the aircraft to a plurality of remote locations comprising the stepsof: detecting aircraft with a radar; identifying the aircraft as friendor foe; encoding and transmitting the position and identity and alertstatus of the aircraft to a plurality of remote locations; receivingsaid encoded position, identity, and alert status of the aircraft;decoding the received information and displaying the received aircraftposition and identity and alert status.
 2. A method as set forth inclaim 1 wherein the step of encoding the position and identity of theaircraft includes the steps of placing a plug in a plugboard to indicatethe position and identity of the aircraft, and encoding the informationshown on the plugboard so it may be transmitted.
 3. A method as setforth in claim 1 wherein the step of displaying the received positionand identity of the aircraft includes the step of lighting a light in amatrix of lights to thereby indicate the position and identity of theaircraft.
 4. A device for transfer of information from a first locationto a plurality of second locations comprising: a plugboard; a first andsecond plurality of plugs for insertion in said plugboard; a codegenerator for encoding the position and identity of said plugs insertedin said plugboard, said first plurality of plugs indicating a friendlyaircraft and said second plurality of plugs indicating a foe; means fortransmitting said encoded position and identity of said aircraft; meansfor receiving and decoding said encoded position and identity of saidaircraft; means for displaying the decoded information indicating theposition and identity of said aircraft.
 5. A device as set forth inclaim 4 wherein said means for displaying the decoded informationcomprises a display panel having a matrix of lights thereon, each ofsaid lights being responsive to the position and identity of said pluginserted in said plugboard whereby the position and identity of anaircraft may be ascertained by viewing said display panel.